I first noticed the flashes of light streaking across the sky at around 11:30, heading into a mountain pass to go up to the Berkeley Hills and Grizzly Peak from Moraga. The light streaked across the sky at a speed 5-10x that of a plane, and looped around several times, ruling out any possibility of a commercial plane. The lights continued to flash across the sky, and were visible from around a 10 mile radius. The instances were frequent but short lived, the streaks would last for one or two seconds at most. I saw the streaks without any doubt in my mind at least 15 counted times. My friend was with me and corroborates the whole thing.